Thermoresponsive device



Nov. 21, 1944- A. s'rocKsTRoM f 2,363,451

4 THERMO-RESPONSIVE DEVICE l Filed Oct. 20, 1941 2 Sheets-Sheet l I fig] f v '42% im n nventor @wm Bg v I Nov. 21, 1944, A) sTocKsTRoM THERMO-RESPONSIVE DEVIC Filed Oct. 20 1941 2 Sheets-Sheet 2 fvlllllllllll'll Jnvehor (Lttorn 95's Patented Nov. 2l, 1944 l. UNITED STATES eATENT oFFlcE THEaMoREsPoNsIvE nEvicE Arthur Stockstrom, StfLouis, Mo., assignor to American Stove Company. St. Louis, Mo., a

corporation of New Jerseyv Application October 20, 1941, Serial No. 415,841

' 1 claim. (ci. 291-3) The present invention relates to thermo-responsive devices and to such class of devices generally rather than specifically but by reason of the invention being particularly suited for and eicient in connection with gas ranges ancl'convT stituting a decided improvement in4 thermostatic heat regulators and fuel control devices for gas ranges the invention is illustrated in the accome panying drawings in connection with gas ranges and described specifically in respect to its use control valves, and in the-'accompanying draw- 'ings a thermostatically operated oven heat control is illustrated as is likewise a thermostatically operated safety valve. 'In connection with both of said devices they are of the so-called liquid type in that a liquid constitutesv the thermal response medium which operates the mechanical parts of the devices to accomplish the desired result.

Thermostatically operated heatl control devices as well as safety valves of the liquid type can and do vary Widely in construction and hence the accompanying drawings are to be considered as merely illustrative of construction and not in any "sense to constitute a limitation of the invencommercially adaptable for use in connection with high temperature work because the thermo-responsive medium of the devices has had too low a decomposition temperature; has had a low boiling point; has had high vapor pressure and high cost; has so greatly restricted the operating temperatures of gas ranges as to curtail undesirably the functions of the ranges; along with other specific objections as will hereinafter ap-v pear.

With devices of the character described as heretoforev known and in use, the thermo-responsive liquid of the devices are quite apt to and frequently do break down or decompose and render the devices inoperative if the thermo-responsive medium is subjected to a temperature in excess of 650 F. It hasv been found that in range ovens, particularly in ranges used in hotels, restaurants and the like, temperatures in excess of 650 F. are'often necessary in order to braise and sear meats.

In many ranges, particularly domestic ranges, a single oven and a single burner, which burner is under the control of the baking oven temperature regulator, are utilized for both baking and broiling operations. to be reached for successful and proper broiling operation is much higher than that utilized in baking operations but since the thermo-respon sive element of the control device is in the combination baking and broiling oven and responsive to the heat generated therein it is often difficult if not impossible, with control devices utilizing tated or confinedk the satisfactory usek of these l devices to temperatures not in excess of 550 F. while it is necessary, as will hereinafter appear, to deal with and control with temperatures which are in excess of.650 F. l

As ageneral statement it can be said that devices of the character here dealt with have in the past been objectionable, inefflcient'and not dering them inoperative.

any of the liquid thermo-responsive mediums heretofore in use, to reach the desired broiling temperature or if it is reached the -life cf the temperature control device is shortened or destroyed by the intense heat to which the thermoresponsive medium of the baking oven temperature control device is subjected. In many instances it is impossible to reach the desired broiling temperature because the thermo-responsive medium sets up a `throttling action on the gas flowing to the combined broiler and baking burner. v

The lives of devices of the character here being discussed as made in the past and at the present time"` are also jeopardized in another manner and which when. it occurs will in the majority of instances completely destroy the devices by rendering them so inaccurate as to amount to ren.-

In the manufacture of ranges the heat control devices are calibrated at the factory andy if fory any reason during use the devices become inaccurate they are rt cali- The temperature necessary brated by service men. Either at the factory or by the service men's carelessness or mistake in setting a calibration by over-adjustment will peruse, this liquid has certain attributes not true y of thermo-responsive liquids as heretofore known. These attributes comprise extremely high boiling points and extremely low melting points taken together with the ability to withstand high temperatures without breaking down or decomposing, all of which assures accuracy and durability of the devices over a greater temperature range than has been possible with thermo-operated devices in the past.

In the drawings, which are illustrative of two specific applications of the inventive thought:

Fig. l is a sectional view through an automatic thermo-responsive heat regulator embodying the present invention.

Fig. 2 is a view, partly in section, illustrating the gas by-pass and illustrating the temprature setting dial of the device.

Fig. 3- is a sectional view of a thermo-operated fuel safety control valve and its application to a gas range.

Fig. 4 is a front view of a heat control dial for the present high temperature device.

Fig. 5 is a heat control dial such as found on l present temperature heat control devices. Y

-It being desirable in domestic ranges and particularly combination oven and broiler ranges and in respect to safety valves to have a thermostatically controlled temperature range greater than the hereinbefore normal range of 250 F.- 550 F., I provide for this by utilizing in the thermo-responsive devices a thermo-responsive medium or liquid of the organo-silicon -group of compounds.

In devices heretofore known and in use it has been common practice to utilize diphenyl compounds as a heat responsive medium but these have the undesirable characteristic of boiling at about 650 F. and if subjected to a temperature in excess of 650 degrees there is grave danger of these compounds breaking down to the extent that the device with which they are used becomes inoperative. Respecting the organo-silicon compound mentioned above, tetracresoxysilane remains liquid even when subjected to temperatures as low as 25 F. below zero and its boiling point is approximately 800 F. The attributes of this material is such that when used as the thermo-responsive medium in a thermo-responsive device said device can be safely used to accurately operate at much higher temperatures than have such devices in the past.

Additionally it has been found that this material will not attack stainless steel,iron, copper or brass, even at high temperatures, and this is a. highly desirable attribute inasmuch, as will appear, the heat-responsive medium is confined within a bulb, tube and bellows which must for practical reasons be made of some metallic material.

Expldning now the particular use of, the aforementioned material as a thermo-responsive medium in a domestic oven automatic ftemperature control device, and referring particularly to Figs. 1 and 2 of the drawings which illustrate a commercially practical liquid type oven heat regulator, A designates a housing to the chamber Ito which fuel is delivered from a suitable source of supply through an inlet 2. Fuel is permitted to pass from the housing chamber I to a larger adjacent housing chamber 3 under the control of a valve 4 which is normally urged towards its seat I by a spring 6. The chamber l delivers fuel to the oven or other burner with which the device is associated through its outlet 1.

Ordinarily the range is equipped with a constant burning pilot light and fuel for said pilot is delivered from the housing inlet chamber I through a pilot outlet opening 8.

Those familiar with automatic oven temperature control are aware that the device being explained acts to control the delivery of fuel to the oven burner when the desired temperature within the oven has been obtained and operate to permit the iiow of fuel to said oven burner until said predetermined temperature is reached and will operate to permit the ilow of fuel after the predetermined temperature has been reached in the oven and then the oven temperature falls off. However it is ordinary practice not to shut on the fuel completely to the oven burner during the use of the oven but to at all times permit a very low fire at the burner. 'I'his is accomplished by providing a bypass and this is designated as an entirety in Fig. 2 of the drawings at B. This bypass comprises a bolt 9 having therein a passageway l0 which is in communication with the fuel inlet chamber I through an opening II. The passageway III of the bolt discharges into the fuel outlet chamber 3 through a suitable nozzle I2.

The regulator housing A and the parts therein can if desired be positioned remote to the oven or other chamber the heat in which is to be controlled but within said oven or chamber there is positioned a metallic bulb C which is connected to an expansible chamber composed of a pair of diaphragms I3 and I3 positioned in the housing by a tube Il.

The chamber, tube and bulb are completely and entirely filled with the thermo-responsive medium tetracresoxysilane and it has been found that to obtain the best and most accurate operation the tube, bulb and chamber should be evacuated and filled with the thermo-responsive -medium under a high vacuum so as to exclude all air.

and there is a complete absence of the generation of any vapor pressure within the closed ysystem which contains the thermo-responsive medium or material.

The' chamber diaphragm I3 is provided with an extending pin or stud I5 having attachment to a disc IB carried in separated relationship to the bottom of a housing .or carrier I1 from which extends a stud or pin I8.

'I'he disc and its housing constitute a compensator to compensate any response or action of the Y which will be conveniently positioned as for in'- stance on the front panel of the range. A dial 22 is associated with the operating handle and will carry on its face temperature indications up toV the maximum temperature range of which the device is capable of operation.

Within the fuel discharge chamber 3 of the n housing a lever 23 at one end bears against the compensator stud or pin I6 and has its other end forked as at 24 to straddle a fixed stem 25 and the valve operating sleeve 26 which is mounted for reciprocation onsaid fixed stem. Interme-V diate its length the lever is fulcrumed on a pin or stud 21 carried by the inner endrof the temperature setting shaft I9.

'I'he valve operating sleeve 26 has one end 28 engaging the valve in opposition to the spring 6 while its opposite end is provided with a head 29 behind the forked end of the lever. Behind the sleeve head 29 a coil spring 30 having a tension greater than that of the .spring 6 tends through -the valve sleeve to normally hold the valve in an open position. i

Thus it will be seen that when the thermo-responsive fluid within the closed system expands it will exert a pressure upon the lever 23 to rock said lever on its fulcrum 21 and move its forked` lits seat, all as is well understood by those familiar with devices of the present nature.

The present device provides for calibration both at the time of manufacture andwhile in use in the field. The temperature dial 22 is geared for rotation with the Aoperating handle 2| and these two parts are held normally in operative engagement under the tension of the coil spring 3l which as abutted against a collar 32. To calibrate or adjust it is only necessary to push the dial inwardly and rotate it keither to the right or to the left in accord with the error to be corrected.

An elongated stop pin 33 is carried by the housing A and is in the path of travel of an extending ear or lug 34 carried on the rear face of the dial 22. This construction willl limit the permissible rotation of the temperature setting portion of the apparatus.

`Figure of the drawings illustrates a conventional temperature dial and temperature setting i handle 35 and it will clearly appear that the temperature setting handle and dial can be moved very little beyond the 550 F. setting and that the Broil" setting is only slightly beyond said highest temperature reading. Figure 4 however which illustrates the present temperature setting dial 22 makes it clear that the temperature can be increased far beyond the 550 degree setting and that the Broil" setting is far removed' "from the 550 degree' indication of the dial. j y

Where automatic ignition is usedV it is common practice to provide a safety valve which will cut oli' the flow of vfuel to the main burner in the event the pilot light burneris not ignited and ready to ignite the main burner.

Figure 3 of the drawings illustrates a construction of this kind and here the oven or other chamber being heated is indicated at E and the constant burning pilotlight at 36.

The principle of operation of the safety valve is similar to the automatic heat regulator and comprises a housing F having therein a fuel inlet chamber 31 and a fuel outlet chamber 38, communication between which is under the control of a valve 39. Fuel from some suitable source of supply is brought to the inlet chamber by a conduit 40 while fuel permitted to pass to the main burner is conveyed thereto from the outlet chamber 38 by avconduit 4l`.

The valve 39 is normally urged towards its seat and a closed position by a spring 42. In this construction there is also provided a collapsible and expansible chamber 43 connected by a capillary tube 44 with a bulb 45 which is disposed in the oven E. vThe chamber, pipe and bulb are completely filled with the particular thermo-responsive medium or material heretofore specifically described.

The bulb is closely associated with the constant vburning pilot light 36 and is preferably provided with a shield 41 to prevent the flame of thepilot light actually playing upon the bulb. This close association however subjects the bulbto an extremely high temperature.

Within the fuel discharge chamber of the housing F a lever 48 is fulcrumed at one end upon an adjustable fulcrum pin 49 and has its remote end 50 forked or bifurcated to straddle a fixed pin 5| upon which is reciprocably mounted a valve engaging and operating ysleeve'52. One end of this sleeve is seated within the valve while its other end is provided with a head 53which is maintained in constantengagement with the end 50 of the lever by the tension exerted by a coil spring 54. The valve seat appears at 55.

The expansible and contractable chamber 43 is provided with an extending pin 56 which en-` gages the lever 48 intermediate its ends.

With the construction thus described it will be seenthat as long as the pilot burner is in operation the thermoresponsive fluid is heated and kept in an expanded condition which will cause the pin 56 of the expanded expansible and contractable chamber 43 to rock the lever upon its fulcrum and exert pressure through the valve operating sleeve 52 to hold the valve in an open position.

Should the pilot light become extinguished and the thermo-responsive medium becomecool the spring 54 willmove the valve operating sleeve and lever in a direction away from thevalve and permit the spring 42 to move the valve to a closed position and thereby prevent the delivery of fuel Vto the main burner.

' Thus it will be seen that this safety valve or device avoids 'the possi-bility of the delivery of fuel to the main burner in the event the pilot light burner is not ignited and ready to ignite the fuel delivered to the main burner.

It will be understood that in a'gas range conthe drawings and specifically hereindescribed v constitute only two of many devices which could embody the present inventive concept and the in- I claim:

In a thermostatically operated device for use over a wide range of temperatures from a low of at least zero degrees F. to a high of approximate- '5 ly800 F., abulbinthe zoneoi heat,anexpansi ble and contractable chamber, a conduit interconnecting thebulb and the chamber, a, thermoresponsive medium completely filling said bulb. conduit and chamber, said thermo-responsive vention accordingly should be limited only within 10 medium being tetracresoxysilane.

` the scope oi' the hereinafter appended claim.

ARTHUR STOCKS-FROM. 

